The invention relates generally to wireless communications systems, and more particularly to self-organizing wireless communication network systems for peer-to-peer communication.
Peer-to-peer communication between two mobile terminals provides a direct link between the two mobile terminals in public land mobile network. When the direct link is established, the dedicated links between the base station and mobile terminals can be disconnected, while the common control channel (CCCH) is maintained. This will save at least two radio channels for the system and reduce the end-to-end delay.
Among existing 3G systems, the TDD CDMA system is the most suitable system for the application of peer-to-peer communication, because the same carrier frequency is used in both uplink and downlink communications, which will simplify the RF module of the mobile terminal. Additionally, the application of peer-to-peer communication technology will overcome some inherent shortcomings of the TDD CDMA system, such as the shortage of spreading code, small coverage, etc. An example of the TDD CDMA system is the TD-SCDMA system, which has gained more popularity in China.
To establish a direct link between two mobile terminals, the two mobile terminals must first be able to properly receive signals from each other. Thus, before establishing the direct link, the two mobile terminals have to test the channel characteristics between themselves. In one scheme, a wireless communication network system allocates a separate channel for the test. After the direct link is established, the network system will allocate additional radio channels for the peer-to-peer communication. However, the channel allocations for these purposes take away valuable radio resources, which are already inadequate. Thus, if the radio resources are used up, a separate channel cannot be allocated for the test. By allocating additional radio channels for the peer-to-peer communication, it also creates complexity in the radio resources re-allocation scheme. Further, since the test is not directly performed on the newly allocated channels between the mobile terminals, there is no assurance that the characteristics of the new channels also meet the requirement for direct communication.
Therefore, there is a need for an improved system for establishing reliable direct links for peer-to-peer communications in a wireless communication system.